1. Field of the Invention
This invention relates generally to surgical instruments and more particularly to a miniature surgical instrument that is adapted to remove ferrous foreign particles from an eye.
2. Description of the Prior Art
Generally speaking, intraocular foreign bodies may classified as either magnetic or non-magnetic. The present invention is directed only to the former type and only that form of prior art will be discussed.
Magnets have been used for some time in the removal of ferrous foreign objects in the eye. However, prior art structures have not been entirely satisfactory. One technique which has been used for many years is to locate the foreign body and to manipulate it by means of a relatively large magnet or electromagnet that is applied outside the eye. When the ferrous particle is brought near the surface an incision is made in the sclera and the particle is removed either by forceps or by the magnet. Several problems are related to this technique. For example, it may be necessary to remove one or more extra-ocular muscles in order to reach the operating site. Furthermore, damage may be done to the retina by removing the body through the wall of the eye, or damage may be done to the vitreous in moving the foreign body within the eye by the external magnet. In addition, it is frequently difficult to determine exactly where to cut the sclera in order to position the extracting tool directly over the foreign body and in such instances it is not uncommon that a larger incision than is absolutely necessary must be made.
The earliest magnets that were used for the purpose of removing a ferrous foreign object from the eye were permanent magnets. However, with such type instruments, it was necessary for the ferrous foreign body to be virtually in contact with the pole tip of the magnet in order to remove the object. In order to determine the efficiency of an electromagnet that is used for the purpose of removing ferrous foreign bodies, the field strength and the gradient of the field strength must be determined. It is well known that the magnetic field of an electromagnet can magnetize a foreign body that is made of ferrous material and which is located in the eye. The gradient of the field strength of the magnet serves to pull the ferrous object towards the pole tip during that portion of time when the ferrous particle approaches the magnet.
Another form of eye repair damage by foreign objects requires the surgeon to work within the eye through a pair of needle insertions that are less than 1 mm. in diameter. In one of the insertions, a bundle of glass fibers conducts light into the eye. Through the other insertion a series of surgical instruments can be inserted to work within the eye. In many cases a jell-like vitreous humor is removed and is replaced with a saline solution. After such a procedure the interior of the eye is optically cleared and the surgeon is able to see inside. When the foreign body is visable, for example it may be resting against the retina, the surgeon can then insert the tip of the probe comprising the present invention through one of the needle holes in the eye and bring it close to the ferrous particle. By pressing the button on the present invention a switch is closed and a coil is electrically energized so as to magnetize the tip of the probe to thereby cause the ferrous foreign body to adhere to the probe. Subsequently the foreign particle can be removed. If further manipulation is required releasing of the button demagnetizes the tip of the probe and the foreign body can easily be transferred to forceps or another instrument.